gd: mr venography
DESCRIPTION
Gd: MR Venography. Martin R. Prince, MD, PhD. Injection Rate. [ Gd] arterial = + [Gd] venous. Cardiac Output. Strategies to reduce Gd Dose. shorten scan duration time bolus for center of k-space digital subtraction higher relaxivity reduce cardiac output - PowerPoint PPT PresentationTRANSCRIPT
Gd: MR Venography
Martin R. Prince, MD, PhD
Strategies to reduce Gd Dose• shorten scan duration
• time bolus for center of k-space
• digital subtraction
• higher relaxivity
• reduce cardiac output
• inject vessel directly
[Gd]arterial = + [Gd]venous
Injection RateCardiac Output
1T1
= R1 • [Gd]
Venous Blood
1T1
= R1
Injection rate
Cardiac output
Arterial Blood
100:1 dilution 50:1
dilution
0.1
0
1
510
20
30
40
5060
100
%Gd:DTPA Contrast Agent Dilution
3D SPGR TR/TE/Flip 6.5/1/45º
TE=1 TE=10
TE=10TE=5
TE=3TE=2TE=1
Conventional Upper Extremity Venography
Radiation exposure
Multiple stations
Variable flow rate
Difficult to time breath holding
Large dose of iodinated contrast
Contrast dilution obscures central veins
• Large caliber iv in forearm
• Elevate arms with cushions
• Coil: • one arm torso coil• two arms body coil
• Sagittal Locator• Coronal 3D Spoiled Gradient Echo• 5cc Gd:DTPA in 250 cc NS (50:1)• Load 2, 60 cc syringes for each arm• Use automatic valve to instantly switch from 1st to 2nd syringe
Landmark
Direct MR Venography Protocol
• Coronal Plane
• Anterior to Clavicle
• Posterior to Right Atrium
• Superior to Mandible
• Use Maximum Field-of-View
• Fast scan to permit breath holding • thick slices (4-5mm)
• zero interpolation (ZIP x 2)
• partial Fourier imaging (0.5 NEX)
Prescription of 3D Imaging Volume
• inject one entire syringe (60 ml)
• Immediately switch to 2nd syringe
• start imaging with breath holding
during injection of 2nd 60ml syringe
Gd injection
Single Operator StrategyInject one arm at a time
Left arm injection
Right arm injection
Two Operator Strategy:
Inject both arms simultaneously
Vessels that are easily accessible
• arm vein
• pedal vein
• umbilical vein
• caput medussa
• brachial artery
• common femoral artery
Summary• IV injection excellent
venograms
• dilute Gd at least 10:1
• inject large volumes
• two 60 ml syringes per arm
• inject rapidly
• breath holding essential
• repeat as necessaryCourtesy of James F. M. Meaney. MD